Field
Embodiments of the present disclosure generally relate to creating planar surfaces on substrates and on layers formed on substrates, and specifically to chemical-mechanical polishing (CMP).
Description of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a wafer substrate, such as a semiconductor substrate or a glass substrate. As layers of materials are sequentially deposited on and removed from the substrate, the uppermost surface of the substrate may become non-planar and require planarization before further lithographic patterning can be patterned thereon. Planarizing a surface, or “polishing” a surface, is a process where material is removed from substrate surface to form a generally even, planar substrate surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess material which has been deposited to fill the features, and to provide an even surface for subsequent lithography-based patterning steps.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique for planarizing substrates. CMP utilizes a chemical composition, typically mixed with an abrasive to form a slurry, for selective removal of material from the surface of a substrate. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly to position a substrate secured therein in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The polishing pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus creates polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition, or slurry, to effect both chemical activity and mechanical activity. The polishing pad has a precise shape to distribute the slurry and contact the substrate. The polishing pad may be cleaned to remove debris which would otherwise collect upon the polishing pad and cause damage to substrates processed therewith and reduce the polishing pad life. Conventional methods of cleaning may in some cases involve directing a de-ionized water (DIW) spray against the polishing pad. The spray often causes slurry and debris to become deposited on the pad and thereby collect in undesirable places resulting in substrate contamination or scratching of later-polished substrates. The spray also can in some cases create a mist, including the debris, which can accumulate in a manufacturing facility to reduce overall cleanliness and scratch later-polished substrates. Reducing the velocity of the spray to better control the debris has a downside of reducing the effectiveness of debris removal from the polishing pad. What is needed are better approaches for cleaning the polishing pad by effectively removing debris while minimizing the potential to contaminate or scratch later-polished substrates.